GI histology - liver and pancreas Flashcards
What is in each corner of a hexagonal lobule?
What is in the middle?
Portal triad, hepatic artery, portal vein and bile duct (plus lymphatic channel).
Central vein in the middle.
Explain the hepatic acinus and each of the zones?
Periportal, intermediate and pericentral.
Explain the function of the hepatocytes?
What are the red arrows showing?
3 cells are tightly opposed.
They are held together by desmosomes.
Lots of microvilli where it faces the sinusoid to increase surface area.
Need lots of RER because they produce a lot of proteins.
Production of bile: raw materials come from blood stream but the bile canaliculus is found in-between the hepatocytes (in case of damage there will be no leakage of bile into the blood stream, it is also why each edge of the bile canaliculus are stapled together by tight junctions as it stops leakage). This is also why the golgi and the Smooth ER is found near this channel.
Also have lipid droplets floating around a long with peroxisomes for detoxification.
Glycogen to release glycogen granules.
This means that the nucleus will be directly in the middle. Some cells have 2 nuclei as they are highly active.
The sinusoid and the hepatocytes are not touching each other and it is the place where the perisinusoidal space exists. The space is maintained by fine collagen fibres which are like pillars. Fibres are produced by stellate cells.
Because the portal vein is taking potentially harmful substances there are special macrophages called kpuffer cells which sit in the liver sinusoid. Has long arms which ‘catch’ bacteria. They also destroy old red blood cells if the spleen is not working.
Red arrows show synthesis of 1) albumin, 2) bile and 3) glycogen
___________ run in the space of disse.
What is the consequence when the liver is unhealthy?
Unhealthy down the bottom.
Cells can die and this starts in zone 3. The remaining cells are relatively healthy.
Stellate cells produce scar tissue where the cells have died, if this happens for a long time then it can cause cirrhosis where it is irreversible.
If this is happening then it also compresses the sinusoid, this increases the pressure in the sinusoid and therefore portal hypertension. Extracellular fluid then leaks out into the lymphatic channels in an exaggerated manner. It can leak so much that it can secrete out of the liver which is called transcapular lymphatic weeping, this causes an enlarged peritoneal cavity and therefore ascites.
Before the bile duct starts there is a small ductule (circled in red). The cells lining the ductule is called a cholangiocyte. These are also the stem cells for liver regenration if needed, this is also a reason why zone 1 can get good regeneration.
Cirrhosis damages which part of the liver?
What does the pancreas look like?
what is the difference?
Pancreas has endocrine bits
Histology of pancreas?
2 major cells of the exocrine pancreas?
Explain diverticula in the small intestine?
Where the duct is entering the duodenum, the wall of the duodenum is deficient.
This creates a weak zone of muscle tissue.
Diverticula is when there is ballooning of the mucosa outward due to weak muscle wall.
What is pancreatitis and the main causes of it.
Inflammation (from alcohol) leads to autodigestion of the pancreas, the secretions of the pancreas are activated inside the organ itself instead of being activated in the duodenum.
Another mechanism: gall stone comes down the tract can get lodged and block the pancreatic juice also, this then causes autodigestion of pancreas.
